Electrostatic finishing is a well-known technology. Generally, it operates on the principle of attraction between oppositely charged particles. Atomized coating material is given a negative charge using high voltage and low current, and directed at a grounded workpiece. Electrostatic spray guns are commercially available from DeVilbiss Ransburg Industrial Liquid Systems, an Illinois Tool Works Company, of Toledo, Ohio, U.S.A.
When electrostatic finishing is employed with non-conductive workpieces, such as wood furniture, the surface of such non-conductive workpiece is wetted to provide a conductive surface. Water is also employed in wood coating with water based paints or lacquers.
However, a number of problems arise when wood is wetted or treated with water based paints or lacquers. First, water based coatings cause the wood grain to rise in the wood, which subsequently requires sanding to restore the wood to a smooth finish. Second, water based coatings require long cure and flash times which demand increased factory floor space compared to coatings requiring shorter cure and flash times. When a wood substrate is coated with several layers, typically three or more, each coating layer must be dried before another coating layer can be applied thereon.
Drying is usually done in large ovens which are generally expensive. Since each coating layer must be dried separately, the cumulative drying time may be significant. The combination of expensive ovens and long drying times makes the finishing procedure expensive and raises the prices of coated furniture and painted substrates.